The present invention relates to a method of operating an internal combustion engine, in particular for a motor vehicle, in which fuel is injected directly into a combustion chamber either in a first mode during a compression period or in a second mode during an induction period, and in which the fuel quantity injected into the combustion chamber is open-loop and/or closed-loop controlled in varying ways in the two modes. Furthermore, the present invention concerns an internal combustion engine, in particular for a motor vehicle, having an injection valve, by which fuel can be injected directly into a combustion chamber either in a first mode during an induction period or in a second mode during a compression period, and having an electronic control unit for the varying open-loop control and/or closed-loop control of the fuel quantity injected into the combustion chamber in the two modes.
Systems of this type for the direct injection of fuel into the combustion chamber of an internal combustion engine are generally known. In this context, a so-called stratified operation, as the first mode, is distinguished from a so-called homogeneous operation, as the second mode. The stratified operation is employed particularly with smaller loads, whereas the homogeneous operation is used for larger loads applied to the internal combustion engine. In stratified operation, the fuel during the compression period of the internal combustion engine is injected into the combustion chamber, specifically into the immediate vicinity of a spark plug. The result is that it is no longer possible to achieve a uniform distribution of the fuel in the combustion chamber, but rather the fuel is immediately ignited by the spark plug. The advantage of stratified operation lies in the fact that the smaller loads that are applied can be handled by the internal combustion engine using a very small quantity of fuel. However, larger loads cannot be managed using stratified operation. In homogeneous operation, which is provided for these types of larger loads, the fuel during the induction period of the internal combustion engine is injected so that it is possible immediately to achieve a swirl effect and thus a distribution of the fuel in the combustion chamber. To this extent, homogeneous operation roughly corresponds to the modus operandi of internal combustion engines in which fuel is commonly injected into the intake pipe.
In both modes, i.e., in stratified operation and in homogeneous operation, the fuel quantity to be injected is open-loop and/or closed-loop controlled as a function of a multiplicity of input variables towards an optimal value with respect to fuel economy, emission reduction, and the like. The open-loop and/or closed-loop control, in this context, is different in the two modes.